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Retrieving jpg from DNG

RW
Rick Womer
Thu, Oct 21, 2021 6:41 PM

I haven’t been around much the last few weeks, largely because I’ve spent a lot of time recovering from an ill-timed massive failure of the external hard drive on which I keep my photos.

A related question (without the long story): I have a few dozen shots in which the DNG file is lost, but the preview jpg is still intact. Is there a way to pull the jpg out of the DNG file? I realized that the resolution won’t be very good, but it’s of snapshot quality anyway.

Took a long photo-walk Tuesday, so i hope to be posting again in the next day or two.

Cheers,

Rick

I haven’t been around much the last few weeks, largely because I’ve spent a lot of time recovering from an ill-timed massive failure of the external hard drive on which I keep my photos. A related question (without the long story): I have a few dozen shots in which the DNG file is lost, but the preview jpg is still intact. Is there a way to pull the jpg out of the DNG file? I realized that the resolution won’t be very good, but it’s of snapshot quality anyway. Took a long photo-walk Tuesday, so i hope to be posting again in the next day or two. Cheers, Rick
JF
John Francis
Thu, Oct 21, 2021 8:47 PM

On Thu, Oct 21, 2021 at 02:41:12PM -0400, Rick Womer wrote:

A related question (without the long story): I have a few dozen shots in which the DNG file is lost, but the preview jpg is still intact. Is there a way to pull the jpg out of the DNG file? I realized that the resolution won???t be very good, but it???s of snapshot quality anyway.

I don't know if there's anything turn-key that can do it (especially if there's a problem with the DNG file).
What, precisely, do you mean by "the DNG file is lost, but the preview jpg is still intact"?
If the DNG file is present (but unreadable) and you can see a preview image, it's quite likely that
you are looking at a cached preview image that your file browser has created, rather than actually
reading the jpg preview from the DNG file.
(You can test this by copying the DNG file to a new location, then pointing your file browser at
that new image location; if you can see a preview image then there's enough of the DNG file left
intact to be able to get at the embedded jpg).

If you can't even read the DNG file, then you're going to be limited to whatever preview image
your file browser created.  That's likely to be at much lower resolution than the original DNG
(on Windows 10, for example, the maximum dimension is limited to 256 - I don't know about Macs).

If you can get at the DNG file, though, you should be able to get the preview jpg embedded in
the file, which is going to be much larger.  It used to be the same size as the full image,
but I haven't actually dug inside a Pentax image file since they switched from TIFF/PEF to DNG.

On Thu, Oct 21, 2021 at 02:41:12PM -0400, Rick Womer wrote: > A related question (without the long story): I have a few dozen shots in which the DNG file is lost, but the preview jpg is still intact. Is there a way to pull the jpg out of the DNG file? I realized that the resolution won???t be very good, but it???s of snapshot quality anyway. I don't know if there's anything turn-key that can do it (especially if there's a problem with the DNG file). What, precisely, do you mean by "the DNG file is lost, but the preview jpg is still intact"? If the DNG file is present (but unreadable) and you can see a preview image, it's quite likely that you are looking at a cached preview image that your file browser has created, rather than actually reading the jpg preview from the DNG file. (You can test this by copying the DNG file to a new location, then pointing your file browser at that new image location; if you can see a preview image then there's enough of the DNG file left intact to be able to get at the embedded jpg). If you can't even read the DNG file, then you're going to be limited to whatever preview image your file browser created. That's likely to be at much lower resolution than the original DNG (on Windows 10, for example, the maximum dimension is limited to 256 - I don't know about Macs). If you can get at the DNG file, though, you should be able to get the preview jpg embedded in the file, which is going to be much larger. It used to be the same size as the full image, but I haven't actually dug inside a Pentax image file since they switched from TIFF/PEF to DNG.
RW
Rick Womer
Thu, Oct 21, 2021 9:50 PM

John,

Thanks for your reply.

What I mean by a lost DNG is a bit embarrassing: I took the card out of the camera, with 171 shots on it. I loaded them into my photo hard drive, removed the card, and then started a backup to a different hard drive. Then I went downstairs.

Not being sufficiently cautious, I then erased the card (but did not reformat it). After dinner I went upstairs again, and was horrified to find my photo hard drive periodically clicking, but clearly comatose. The backup hadn’t begun. Aargh!

The next day (on the advice of a friend who works with Macs for a living, and whose wife is a pro photog), I downloaded a utility ($99) to try to recover the contents of the card; a couple of free alternatives couldn’t find anything. It recovered intact, usable, like-new DNGs for about half of the shots; and for the other half there is only a low-rez JPG. In Lightroom, these show up as blank white, until the software gets around to filling the frame with the JPG.

There are about a dozen shots that I’d really like to have in some form. If there’s no easier way, I’ll put my camera on a tripod in front of the monitor, and photograph the photos.

Rick

On Oct 21, 2021, at 4:47 PM, John Francis johnf@panix.com wrote:

I don't know if there's anything turn-key that can do it (especially if there's a problem with the DNG file).
What, precisely, do you mean by "the DNG file is lost, but the preview jpg is still intact"?

John, Thanks for your reply. What I mean by a lost DNG is a bit embarrassing: I took the card out of the camera, with 171 shots on it. I loaded them into my photo hard drive, removed the card, and then started a backup to a different hard drive. Then I went downstairs. Not being sufficiently cautious, I then erased the card (but did not reformat it). After dinner I went upstairs again, and was horrified to find my photo hard drive periodically clicking, but clearly comatose. The backup hadn’t begun. Aargh! The next day (on the advice of a friend who works with Macs for a living, and whose wife is a pro photog), I downloaded a utility ($99) to try to recover the contents of the card; a couple of free alternatives couldn’t find anything. It recovered intact, usable, like-new DNGs for about half of the shots; and for the other half there is only a low-rez JPG. In Lightroom, these show up as blank white, until the software gets around to filling the frame with the JPG. There are about a dozen shots that I’d really like to have in some form. If there’s no easier way, I’ll put my camera on a tripod in front of the monitor, and photograph the photos. Rick > On Oct 21, 2021, at 4:47 PM, John Francis <johnf@panix.com> wrote: > > I don't know if there's anything turn-key that can do it (especially if there's a problem with the DNG file). > What, precisely, do you mean by "the DNG file is lost, but the preview jpg is still intact"?